Coupling vibration characteristics of rock mass and energy-absorption bolt and its anti-impact mechanism

In order to improve supporting effectiveness of bump-prone roadways,the energy-absorption bolt was inven- ted,which consists of energy absorption sleeve with built-in hex pipe,whorl-steel bolt with friction roller on the head, pre-stressed strand and energy absorption devices at bolt tail. Then the three-dimensional axis-symmetry model of ener- gy-absorption bolt and surrounding rock affected by impact loads was established by simplifying the energy-absorption sleeve as spring and damper situated on the end of bolt parallelly. An analytical solution of displacement impedance function was obtained by analyzing the dynamic response of the bolt top under the coupling vibration of energy absorp- tion bolt and surrounding rock with viscous damping. Then the parameter sensitivity analysis of three-dimensional axis- symmetric mechanical model was carried out. The results show that with the greater parameters such as viscous damp- ing and strength of surrounding rock,anchored length and damping of energy-absorption bolt,the greater complex stiffness and resistance ability for deformation of supporting system can be achieved. Energy-absorption sleeve can absorb part of impact energy acting on bolted rock mass,the full length anchorage of post-grouting enhances the ability of sup- porting system to resist longitudinal deformation,absorption device at bolt tail can subduct the reflected tension effect of shock wave. The stability of the system under the action of impact load are improved significantly. And the cushio- ning,vibrations resistance and wave-absorbing mechanism of support system was revealed preliminary.